The present invention relates to systems for limiting the speed of a vehicle which may serve as a driving aid and which are of the type which incorporates over-ridable return means which raise a main speed-controlling member, typically a gas or accelerator pedal, with a limited force of at least a predetermined amount as soon as the speed of the vehicle exceeds a predetermined speed.
A driver travelling along a road at a limited speed may be induced to exceed this speed voluntarily or involuntarily. It is, therefore desirable, for obvious reasons of safety, for there to be a device which calls him back to order, bearing in mind that at the present time he has only his speedometer to allow him to judge his speed.
Devices are known which give the driver a visible or audible warning that he has exceeded a predetermined speed. As an example may be mentioned the systems which measure the engine speed by counting the cyclic rate of the ignition. An alarm is triggered at a certain engine-speed which, via the transmission, corresponds to a certain speed of the vehicle. This has the defect that it only holds good for top gear.
Other types of equipment detect the position of the speedometer needle. The accuracy of such systems is entirely relative and they are awkward to adjust quickly when changing from one governing speed to another.
There are also certain methods which employ direct action on the engine independent of the driver, such as cutting out the ignition or completely closing the butterfly valve controlling the fuel mixture being admitted.
The invention has as an object to enable the speed of a vehicle to be limited in a manner which is independent on, or independent of, the driver, so as to make traffic safer the to meet the requirements of various regulations.